Humidification system

ABSTRACT

The present invention provides a method and apparatus for reducing condensation in a respiratory circuit during a delivery of humidifying agent into the respiratory circuit. A first amount of humidification agent to a first volume of gas is delivered to a patient respiratory circuit during a patient inhalation cycle or immediately after a patient exhalation cycle, and the humidification agent or the first volume of gas is heated. Condensation is removed from the respiratory circuit at least in part by providing, during a patient exhalation cycle or immediately after a patient inhalation cycle, a second amount of the humidification agent to a second volume of gas being delivered from the gas source to the patient respiratory circuit, the second amount of the humidification agent being significantly less than the first amount of the humidification agent.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 15/018,163, entitled “HUMIDIFICATION SYSTEM,” filedon Feb. 8, 2016, which is a continuation application of U.S. patentapplication Ser. No. 12/952,658, entitled “HUMIDIFICATION SYSTEM,” filedon Nov. 23, 2010, now U.S. Pat. No. 9,314,582. The disclosure of theseapplications are hereby incorporated by reference in their entirety forall purposes.

FIELD OF THE INVENTION

Aspects of the present invention relate to humidification systems whichprovide humidified gas to a patient.

BACKGROUND OF THE INVENTION

Humidification systems have long been used to treat patients in need ofrespiratory assistance. A typical humidification system generallyincludes a source of gas, a source of water vapor, and a deliverysystem. In the typical humidification systems, the water vapor is firstproduced by heating a stationary body of water contained in ahumidifying chamber. Then, the water vapor mixes with gases passingthrough the humidifying chamber, thereby humidifying the gas. However,heating the body of water to a point sufficient to produce water vaporcan take a significant amount of time, depending on the amount of watercontained in the chamber. In the stationary water humidifier, thehumidifying chamber containing the water is arranged so that the watervapor mixes with the gas flowing through the humidifying chamber,thereby humidifying the gas. Furthermore, because the stationary wateris heated, when the gas passes over the heated water, the gas is alsoheated. Thus, a heating step occurs simultaneously with the humidifyingstep. The humidified gas then proceeds through a respiratory circuit,which directs the humidified gas to a patient. U.S. Pat. No. 5,445,143discloses such a system.

It is known to implement a stationary water humidifier in a humidifyingsystem having parallel gas flow paths. U.S. Pat. No. 7,146,979 disclosessuch a system. In particular,

U.S. Pat. No. 7,146,979 discloses a humidification system having a valvefor splitting a gas into two different paths, wherein one path ishumidified while the other is heated by a heater. The system is capableof adjusting the valve to control the relative humidity of the gas beingdelivered to the patient. However, operating the system in this mannerrequires implementing sensors for determining relative and absolutehumidity of the gas.

Other humidification systems may meter a flow of water to an evaporator.U.S. Pat. No. 6,102,037 describes such a system. The system disclosed inU.S. Pat. No. 6,102,037 provides water vapor with a temperature above134° C., which heats the respiratory gas. Another humidification systemhas been disclosed that avoids pumping water and reduces the timerequired to heat the water by using a capillary system. For example,U.S. Pat. No. 7,694,675 uses a low porosity sintered glass or ceramic todraw water to and through an evaporator tube, where the water isevaporated into a gas.

Regardless of the type of humidifier used, conventional humidifyingsystems implement a respiratory circuit to provide a flow path from thehumidified gas to the patient. Many of the known humidification systemsare capable of delivering over 100 Watts to evaporate the water.Therefore, it is preferable to locate the evaporating components awayfrom the patient to simplify system design and minimize patient risk.Furthermore, it would not be comfortable for the patient to have bulkyequipment located directly by the patient's face. It is also importantto ensure the gas flow being received by the patient arrives at a safetemperature, which is capable of being measured and controlled. Byproviding a respiratory circuit extending from the humidifier to thepatient, the above problems are avoided. However, using a respiratorycircuit to deliver the humidified gas creates additional problems.

A significant problem that occurs when using a respiratory circuit todeliver humidified gas is the formation of condensation in therespiratory circuit. Condensation, or “rainout,” occurs due to thetemperature gradient existing between the respiratory circuit and theexternal temperature of the patient's room. The ambient room temperatureis generally lower than the temperature of the gases inside therespiratory circuit because the patient's room is usually maintained ata comfortable level for the patient. As humidified gas flow passeswithin the relatively colder walls of a respiratory circuit, a certainamount of water vapor will condense along the walls of the respiratorycircuit. After too much condensation builds up, a practitioner mustmanually remove the condensation from the respiratory circuit because itis dangerous for a patient to accidentally inhale liquid. The manualremoval of condensation requires taking apart the respiratory circuit orreplacing the respiratory circuit, which can take a substantial amountof time. Taking down the circuit to remove condensation breaks thecontinuity of delivering humidified gas to the patient. Furthermoreopening the circuit to remove condensation causes a loss of respiratorypressure support and may result in alelactasis or respiratory distress.

Several of the known humidification systems attempt to solve the problemby providing heated elements within the respiratory circuit itself. Byselectively heating the heated elements, the operator maintains atemperature of the heated walls to maintain the temperature of the gasabove the dewpoint, thereby potentially reducing condensation. Such asystem is disclosed in U.S. Pat. No. 7,146,979. However, as discussed inU.S. Pat. No. 6,078,730, in such a system, the temperature is highestclose to the wire, but low on the wall across from the heater, therebyallowing condensation to occur. To improve on this system, U.S. Pat. No.6,078,730 discloses an alternative humidification system that includes aheater wire sitting against or adjacent to an internal wall of arespiratory conduit. Furthermore, DE 4312793 discloses a humidificationsystem having a heater provided in a respiratory circuit. However, thesesystems require additional heated elements and controls to heat therespiratory circuit walls and the gas to reduce the condensation.

Thus, there is a need in the art for a simple method for reducingcondensation in a respiratory circuit.

SUMMARY OF THE INVENTION

The present invention provides a method of reducing condensedhumidifying agent in a humidification system, the method includesproviding a humidification system having a respiratory circuit fordelivering a volume of gas to a patient and a humidifier portion fordelivering a humidifying agent to the volume of gas, pulsing a deliveryof the humidifying agent to the volume of gas at a pulsed interval viathe humidifier portion, heating the volume of gas, and vaporizing,during a non-pulsed interval, condensed humidifying agent present in therespiratory circuit to reduce the condensed humidifying agent present inthe humidification system.

The present invention also provides a method of delivering a humidifiedvolume of gas to a patient, the method including providing ahumidification system having a respiratory circuit for delivering thevolume of gas to a patient and a humidifier portion for delivering ahumidifying agent to the volume of gas, providing the humidifying agentat a controlled flow rate to the humidifier portion via a humidifyingagent input line, vaporizing the humidifying agent via a heated element,delivering the humidifying agent to the volume of gas, therebyhumidifying the volume of gas, heating the gas flow, and delivering thehumidified volume of gas to the patient via the respiratory circuit.

The present invention also provides a humidification system for carryingout the method of reducing condensed humidifying agent and the method ofdelivering humidified gas.

The above and still other advantages of the invention will be apparentfrom the detailed description and drawings. What follows are one or morepreferred embodiments of the present invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic overview of a humidification system;

FIG. 2 is a schematic view of a first aspect of the humidificationsystem of FIG. 1;

FIG. 3 is a schematic view of a second aspect of the humidificationsystem of FIG. 1; and

FIG. 4 is a schematic view of a third aspect of the humidificationsystem of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method of removing condensedhumidifying agent from a humidification system, a method of deliveringhumidifying gas to a patient, and a humidification system for performingthe methods. It is to be understood that the term gas is intended toinclude any gas suitable for use with the following disclosure. Forexample, the gas may comprise oxygen, ambient air, or any otherbreathable gas. The method of removing condensed humidifying agentincludes pulsing the delivery of a humidifying agent to a heated volumeof gas as the volume of gas travels towards the patient and evaporatingthe condensed humidifying agent during a non-pulsed interval. The methodof delivering humidified gas to the patient includes delivering acontrolled amount of humidifying agent to a humidifier portion. Thus,the present invention effectively and easily allows a practitioner toreduce condensation present in a humidification system by removingcondensation. Furthermore, the present invention also provides analternative to a humidifier having a stationary water chamber.

FIG. 1 illustrates a schematic overview of an exemplary humidificationsystem in which the inventive methods may be implemented. Thehumidification system 100 includes a gas source 110 in communicationwith a respiratory circuit 120 and a humidifying portion 130. Thehumidifying portion 130 is also in communication with the respiratorycircuit 120 at a point downstream of the gas source 110. The gas source110 may be any suitable device that provides a flow of gas to beprovided to a patient, such as a lung ventilator. The humidifyingportion 130 includes a device capable of providing a humidifying agentto the gas flow as the gas flow travels through the respiratory circuit120. Exemplary aspects of the humidifying portion 130 are provided inmore detail herein. The respiratory circuit 120 delivers the humidifiedgas having humidifying agent to a patient 140. Throughout thisdisclosure, the term “humidifying agent” is intended to encompass anyagent capable of humidifying the flow of gas. It should also beunderstood that the humidifying agent may be any agent that may bedelivered to a patient via an inhaled volume of gas, includingaerosolized or vaporized medicine. In one aspect of the invention thehumidifying agent comprises water. The respiratory circuit 120 alsoprovides an exhaust path for gas being exhaled by the patient.

In the exemplary aspects described herein, the humidifying portion 130vaporizes the humidifying agent and delivers the vaporized humidifyingagent to the volume of gas. The volume of gas provided to therespiratory circuit 120 is generally dryer and colder relative to thelater humidified state when the gas is first provided from the gassource 110. The gas flow is heated at one or more of the followingpoints in flow path: before passing through the humidifying portion 130,while passing through the humidifying portion, and after exiting thehumidifying portion 130. Thus, when the humidifying agent is deliveredto the volume of gas via the humidifying portion 130, the volume of gasbecomes more humid, while the heating step ensures the humidifying agentis in a vapor state, thereby making the gas safe for breathing. Therespiratory circuit 120 is also in communication with the patient 140 ata point downstream of the humidifying portion 130. Thus, after thehumidifying agent is delivered to the volume of gas, the humidifiedvolume of gas reaches the patient 140 and is inhaled by the patient 140.The patient then exhales through an exhaust portion of the respiratorycircuit 120. The exhaust portion may lead back to the gas source 110.

In an exemplary aspect of the present invention, the humidifying portion130 is operated to pulse the delivery of humidifying agent to a volumeof gas flowing through the respiratory circuit 120. The gas source 110is configured to provide a volume of gas corresponding to a patient'snormal breathing volume. More specifically, the humidifying portion 130is operated to quickly increase the delivery of humidifying agent to thevolume of gas that is being delivered to the patient 140. During patientexhalation, the gas source 110 provides a second volume of gas,alternatively referred hereinafter to as a bias volume. At a time whenit is desirable to remove condensation from the respiratory circuit 120,i.e., when the bias volume of gas is being delivered, the humidifyingportion 130 is operated so that less humidifying agent is delivered tothe bias volume of gas as compared to the pulsed delivery of humidifyingagent to the inhaled volume of gas. Because the bias volume of gas hasless humidifying agent as it passes through the respiratory circuit 120,the bias volume of gas will vaporize condensed humidifying agent presentin the respiratory circuit 120. Thus, in the non-pulsed interval, theflow of the bias volume of gas effectively removes condensed humidifyingagent from the respiratory circuit 120. As will be described in moredetail herein, in one aspect the pulse may be provided by directing avolume of gas toward the humidifying portion 130, while in anotheraspect the pulse may be provided by controlling the rate of flow ofhumidifying agent into the humidifying portion 130.

In an aspect of the present invention, the timing of the pulse may beset according to the breathing pattern of the patient 140. For example,because it is desirable for the patient to receive the humidified gasduring inhalation, the humidifying portion 130 may be operated to pulsethe delivery of humidifying agent to a volume of gas at the start ofinhalation or immediately following patient exhalation. Likewise, it isnot desirable for the patient 140 to inhale a non-humidified gas stream.Therefore, in an aspect of the present invention the humidifying portion130 may be operated to provide humidifying agent to a bias volume of gasin the non-pulsed state during patient exhalation or immediately afterpatient inhalation. By delivering the pulse in the above-describedmanner, the patient 140 will preferentially receive humidified gas wheninhaling and the respiratory circuit 120 may be cleared of condensationat other times.

Additionally, the timing of the pulse may be set so that the volume ofgas containing a pulsed amount of humidifying agent is present in somepart of the respiratory circuit 120 at the same time a bias volume ofgas containing a non-pulsed amount of humidifying agent is present inanother part of the respiratory circuit 120. For example, a bias gas maybe delivered to the respiratory circuit 120 from the gas source 110, towhich a non-pulsed amount of humidifying agent is delivered. Immediatelyfollowing, while the non-pulsed bias volume is traveling throughrespiratory circuit and evaporating condensation, a volume of gas towhich the pulsed amount of humidifying agent is delivered, is providedto the respiratory circuit. Accordingly, the condensation is beingevaporated while the volume of gas receiving a pulsed amount ofhumidifying agent is traveling through the respiratory circuit. It isalso within the scope of the invention that under certain circumstancesthe bias volume receiving the non-pulsed delivery of humidifying agentmay be delivered the patient. The non-pulsed bias volume may bedelivered to the patient when the amount of condensation present in therespiratory circuit 120 is great enough that the bias volume ultimatelyends up being adequately humidified as the gas travels through therespiratory circuit 120.

The method of delivering humidified gas to a patient 140 also uses theabove-described components of the humidifying system 100. The methodprovides a manner of delivering a controlled amount of humidifying agentto the gas stream, thereby avoiding the problems associated with astationary water humidifier, while allowing precise control of theamount of humidifying agent delivered to the dry gas. As with the methodof reducing condensed humidifying agent, in the method of deliveringhumidified gas, the volume of gas flowing from the gas source 110 isheated to the proper temperature to ensure the humidifying agent isvaporized before reaching the patient. The heating step may be performedas described above, i.e. before, after, or simultaneous with thehumidifying step. Also as described above, the volume of gas flows tothe humidifying portion 130 of the humidification system 100 where thehumidification of the volume of gas occurs. In an exemplary aspect ofthe present invention, instead of including a stationary waterhumidifier, the humidifying portion 130 includes a flow controller thatcontrols delivery of the humidifying agent to a heated element. The flowcontroller may be operated and controlled to provide a particular flowof humidifying agent to the humidifying portion 130. More specifically,by optimizing the flow of humidifying agent delivered to the humidifyingportion 130, the amount of humidifying agent delivered to the volume ofgas may be precisely controlled. As discussed in more detail herein, theother variables may be controlled, such as, but not limited to, freshgas flow rate and heated element temperature. Furthermore, by deliveringhumidifying agent to a heated element, the above-described disadvantagesof the stationary water humidifier are avoided. In particular, asdiscussed in more detail herein, by delivering humidifying agent, theheating step and the humidifying step will not occur simultaneously,thereby allowing more flexibility in controlling the system.

Several exemplary aspects of the humidifying portion will now bedescribed. FIG. 2 illustrates a first exemplary aspect of thehumidifying portion 200. The humidifying portion 200 includes astationary humidifying agent humidifier 210 and a diverter 220 fordiverting a volume of gas. The diverter 220 may include any apparatuscapable of partially or entirely diverting the flow of a volume of gastraveling from a gas source 110, through a gas inlet line 270, into ahumidifying flow path 230 and a diverted flow path 240. As shown in FIG.2, in an exemplary aspect, the diverter 220 is a valve. The valve may bea simple toggle valve that directs the entire flow to the humidifyingflow path 230 and the diverted flow path 240, or it may allow for aparticular ratio split between the humidifying flow path 230 and thediverted flow path 240. For example, the diverter 220 may be capable ofsplitting the gas flow from anywhere between 100% of the flow in one ofthe flow paths and 0% in the other to 50% in both paths. In order tofacilitate precise control of the diverter 220 a controller 250 may becoupled to the diverter 220.

As described above, when allowing the volume of gas to travel throughthe humidifying flow path 230, the volume of gas will pass through achamber of heated stationary humidifying agent 210. As the volume of gaspasses through the chamber, the volume of gas will absorb humidifyingagent vapor and will be heated. For the reasons described above, afterthe humidified gas exits the humidifying portion 200, condensation maylikely form in a discharge line 260 that is positioned downstream of thehumidifying portion 200. In the case where at least some volume of gaspasses through the humidifying flow path 230, in addition to the heatingof the gas as it passes through the chamber of heated stationary water,the volume of gas may be heated upstream in the gas inlet line 270and/or downstream in the discharge line 260. In the case where at leastsome volume of gas is passing through the diverted flow path 240, thegas may additionally be heated in the diverted flow path 240. The gasinlet line 270, the diverted flow path 240, and the discharge line 260may each include a heating element (not shown), such as a heating wire,to facilitate the additional heating. The heating elements may be usedto ensure that the humidifying agent present in the volume of gasremains in a vapor state upon delivery to the patient. The heatingelement in the diverted flow path 240 may be used to increase thetemperature of the volume of gas passing through the diverted flow path240, thereby facilitating removal of condensation from the dischargeline 260. Furthermore, when heating is carried out in the discharge line260, the heating step may be used in conjunction with the pulsing methodto further reduce condensation.

To remove the condensation from the discharge line 260, the diverter 220may be actuated to divert the gas flow between the diverted flow path240 and the humidifying flow path 230 in pulsed intervals. In thesimplest aspect, when humidified gas is desirable, the controller 250can actuate the diverter 220 to immediately direct all of a volume ofgas through the humidifying flow path 230. Because the valve waspreviously directing all of a volume of gas through the diverted flowpath 240, the amount of humidifying agent delivered to the volume of gasis increased, as compared to the previous volume of gas passing throughthe system. After the humidified gas has been delivered to the patient140, and it becomes desirable to remove any condensation that has formedin the discharge line 260, the controller 250 can immediately actuatethe diverter 220 to direct all of the volume of gas through the divertedflow path 240. Because all the gas is being directed through thediverted flow path 240, the amount of humidifying agent delivered to thevolume of gas is decreased, as compared to the previous volume of gaspassing through the system. Thus, by switching the diverter 220 betweenthe two paths, the delivery of humidifying agent to the gas flow ispulsed. Furthermore, in another aspect, the above-described concept canbe applied to any degree of flow splitting. For example, during thepulsing step a volume gas may be divided between the humidifying flowpath 230 and the diverted flow path 240 such that 25% of the volume ofgas passes through the diverted flow path 240 and 75% of the volume ofgas passes through the humidifying flow path 230. In such a case thedelivery of humidifying agent to the total volume of gas is being pulsedas compared to the opposite split (i.e. 25% of the volume passingthrough the humidifying flow path 230 and 75% passing through thediverted flow path 240). The above-described ratios are merelyexemplary, and it is within the scope of the invention that any ratio ofsplit may used, as long as the amount of humidifying agent delivered tothe volume of gas is increased (i.e. pulsed) as compared to a volume ofgas (i.e. a bias volume) that is intended to remove condensation.

As shown in FIG. 2, it is desirable for the diverted flow path 240 torejoin the discharge line 260 near the humidifying portion 200 so thatthe dry gas will pass through a majority of the discharge line 260,thereby maximizing the vaporization of condensed humidifying agent.Furthermore, the controller 250 may be configured to actuate thediverter 220 in accordance with the patient's inhalation and exhalationto optimize the delivery of humidified gas and the removal of condensedhumidifying agent present in the discharge line 260. In an aspect of thepresent invention, the operation of the diverter 220 and theintroduction of gas from the gas source 110 may be timed so that avolume of gas passes through the humidifier portion 200 at the same timethat a bias volume of gas passes through an expiratory limb 290. Asdescribed above, due to the volume capacity of the respiratory circuit,the timing of delivery of a bias volume of gas or a volume of gas to behumidified may be set such that one of the gas volumes immediatelyfollows the other while the first volume (whether bias or humidified) isstill in the circuit. For example, while the bias volume of gas isclearing out condensation in the discharge line 260 or in the expiratorylimb 290, the volume of gas to be humidified may be simultaneouslyentering the humidifying portion.

The controller 250 may communicate with a variety of feedback sensors280, 282, 284, 286 to provide optimal timing of the delivery of pulsedhumidifying agent to a volume of gas. In particular, sensor 280 maydetect a flow rate of gas, sensor 282 may detect a temperature and flowrate of gas passing through the humidifying flow path 230, sensor 284may detect the humidifying agent water level, temperature, and number oftimes the chamber has been refilled with humidifying agent, and sensor286 may detect the temperature of the gas passing through the dischargeline 260. In some aspects, the gas source 110 and the controller 250 maybe preconfigured to communicate with each other such that the controller250 receives timing/breathing pattern information from the gas source110, such as when the gas source is a lung ventilator. When thecontroller 250 and gas source 110 communicate in this manner, it is notnecessary to use the flow sensor 280. However, when controller 250 andthe gas source 110 are not preconfigured to communicate with each other,the flow sensor 280 is necessary to control the system. Notably, in theaspect of FIG. 2, it is not necessary that any of the sensors detectrelative or absolute humidity when supplying humidifying agent to avolume of gas because the pulsing of the humidifying only occurs for abrief moment. However, it is also within the scope of the invention thatthe sensors could detect relative and absolute humidity to assist inoptimizing the delivery of humidified gas.

FIGS. 3 and 4 illustrate additional aspects of the humidifying portion.Unlike the aspect of FIG. 2, the aspects of FIGS. 3 and 4 do not includea stationary humidifying agent humidifier or a diverter. Rather, thehumidifying portion 300, 400 achieves the pulsing step throughcontrolling a flow rate of humidifying agent, thereby controlling theamount of humidifying agent that reaches the volume of gas.

In the aspect of FIG. 3, as with the aspect of FIG. 2, gas travels fromthe gas source 110 through a gas inlet line 390, through a humidifyingportion 300, through a discharge line 365, and to a patient 140. As withthe aspect of FIG. 2, the gas may be heated upstream of the humidifyingportion 300 in the gas inlet line 390 (heater not shown), in thehumidifying portion 300, or downstream of the humidifying portion in thedischarge line 365 (heater not shown). As discussed above, maintainingthe gas at a proper temperature ensures that the humidifying agentremains in a vapor state upon reaching the patient. In the aspect ofFIG. 3, however, in place of a stationary humidifying agent humidifier,the humidifying portion 300 includes a heated element 320 incommunication with a humidifying agent inlet line 350. In the exemplaryaspect illustrated in FIG. 3, the humidifying agent inlet line 350includes a flow controller, such as, a pump 340 for pumping thehumidifying agent from a humidifying agent source 310 to the heatedelement 320. It is also within the scope of the invention, however, thatthe pump may be replaced with any suitable metering apparatus, such asgravity feeding in conjunction with a valve. Therefore, it is to beunderstood that all references to a “pump” or “pumping” includes anysuitable metering device.

The heated element 320 is maintained at a temperature sufficient tovaporize the humidifying agent as soon as the humidifying agent comesinto contact with the heated element 320. The heat from the heatedelement may be sufficient to heat the gas to the necessary temperature,in which case upstream and downstream heaters would not be necessary.The heated element 320 may be made of any material that is suitable ofachieving this function. In an exemplary aspect, the heated element 320may comprise a porous mass of thermally conductive material. Morespecifically, the heated element 320 may comprise a thermally conductivefiber wool or sintered particulate mass manufactured from, for example,copper or stainless steel. The heated element 320 may be enclosed withina heater coupling 370 to maintain the temperature of the heated element320.

In operation, unlike the aspect of FIG. 2, in the aspect of FIG. 3, thegas flow will always pass through the humidifying portion 300. In theaspect of FIG. 3, the pulsing step is achieved by controlling the flowrate of the humidifying agent via the pump 340 or another suitablemetering apparatus. When it is desirable to have humidifying agentdelivered to the gas inlet line 390, the pump 340 or metering devicewill deliver humidifying agent directly onto the heated element 320.Upon contacting the heated element 320 the humidifying agent willvaporize and enter the gas inlet line 390. When it is desirable to havea dry volume of gas (i.e. a bias volume of gas) sent through therespiratory circuit, the pump 340 will be stopped and the humidifyingagent will no longer contact the heated element 320, thereby preventingthe flow of humidifying agent into the gas inlet line 390. When it isdesirable to again provide humidified gas to the patient, the pump 340may be restarted, thereby creating a pulsed delivery of humidifyingagent. Furthermore, similar to the ratio split of the diverter in theaspect of FIG. 2, the rate of pumping or metering humidifying agent maybe increased to produce the pulsed delivery, rather than turning thepump 340 on or off. For example, when it is desirable to providehumidifying agent to the gas inlet line 390, the pumping rate may beimmediately increased to provide an increase in delivery of humidifyingagent, after which the pump 340 will immediately return to the previousor lower flow rate. Thus, the delivery of humidifying agent is pulsed.

As with the aspect of FIG. 2, the pulse and delivery of a volume of gasmay be timed with patient inhalation while the non-pulsed period istimed with patient exhalation. Thus, the aspect of FIG. 3 also reducescondensed humidifying agent present in the discharge line 365 that isdownstream of the humidifying portion 300 when the dry bias volume ofgas passes through the discharge line 365 during the non-pulsedoperation. Additionally, as with the aspect of FIG. 2, the timing of thedelivery of the volume of gas and pulse operation may be set so that adry volume of gas is passing through the discharge line 365 orexpiratory limb 395 at the same time a volume of gas to be humidified ispassing through the humidifying portion 300.

Furthermore, a controller 360 and sensors 380, 382, 384, 386 may beimplemented in a similar manner as in the aspect of FIG. 2 in order todetect relevant system parameters and control the flow of gas andhumidifying agent in an optimal manner. In particular, the pump 340 maybe controlled by a controller 360 to allow for precise timing of thepulses and the gas source 110 may be controlled to time the delivery ofa volume of gas. Sensor 380 may be implemented to detect temperature andflow rate of the gas being delivered from the gas source 110, sensor 382may be implemented to detect flow rate, temperature, and pressure of thehumidifying agent being delivered to the heating element, sensor 384 maybe implemented to detect the temperature of the heating element 320, andsensor 386 may be implemented to detect the gas flow rate, gastemperature, relative humidity, and absolute humidity in the dischargeline 365. The sensor 384 may comprise a thermocouple coupled with theheated element 320. The controller 360 may use some or all of the datadetected from the various sensors to provide optimal control of any ofthe controllable parameters such as volume and rate of gas beingdelivered from the gas source, flow rate of humidifying agent to theheated element, and temperature of the heated element.

The aspect of FIG. 4 illustrates a second alternative to the stationaryhumidifying agent humidifier of FIG. 2. Like the aspect of FIG. 3, theaspect of FIG. 4 provides a pulsed delivery of humidifying agent withoutdiverting the volume of gas delivered to the system. As with the aboveaspects, gas travels from the gas source 110 through a gas inlet line430, through a humidifying portion 400, through a discharge line 490,and to a patient 140. As with the aspect of FIGS. 2 and 3, the gas maybe heated upstream of the humidifying portion 400 in the gas inlet line430 (not shown), in the humidifying portion 400, or downstream of thehumidifying portion in the discharge line 490 (not shown). As discussedabove, maintaining the gas at a proper temperature ensures that thehumidifying agent remains in a vapor state upon reaching the patient. Asillustrated in FIG. 4, the supply of humidifying agent to thehumidifying portion 400 is similar to that in the aspect of FIG. 3. Ahumidifying agent source 410 stores humidifying agent that is pumpedthrough a humidifying agent inlet line 450 via a pump 440. Thehumidifying agent is pumped to the humidifying portion 400. It is alsowithin the scope of the invention, however, that the pump may bereplaced with any suitable metering apparatus, such as gravity feedingin conjunction with a valve.

In the aspect of FIG. 4, the humidifying portion 400 includes a dropletgenerating device 470. The droplet generating device 470 may be anysuitable apparatus that will produce fine droplets of humidifying agent.In an exemplary aspect of the present invention, the droplet generatingdevice 470 comprises an ultrasonic vibrating plate. The plate vibratesat an ultrasonic frequency such that when the humidifying agent contactsthe plate, the fluid is nebulized into very fine droplets. Thenebulizing step also forces the droplets towards the flow of heated gasthat is traveling toward the patient 140 through the gas inlet line 430.Any droplet generating device suitable for producing fine droplets maybe implemented in the aspect of FIG. 4. For example, U.S. Pat. No.4,159,803 discloses ultrasonic aerosol generation via an ultrasonicnebulizer, the disclosure of which is hereby incorporated by reference.U.S. Pat. No. 5,518,179 discloses ultrasonic aerosol generation using aplate with a plurality of small perforations, induced to vibrate atultrasonic frequencies such as to eject droplets of liquid from a liquidreservoir on one face to a gas volume on the opposing face, thedisclosure of which is hereby incorporated by reference. Additionally,U.S. Pat. No. 7,267,121 discloses producing an aerosol via a nebulizerinto a gas flow, the disclosure of which is hereby incorporated byreference. The aerosol generating devices disclosed by these referencesmay be implemented as the droplet generating device 470.

Unlike the above-described aspects, the humidifying portion 400 does notconvert the humidifying agent to vapor before it reaches the volume ofgas passing through the humidifying portion 400. Rather, the finedroplets, which are still in a liquid state, are delivered to the gasinlet line 430 and are vaporized within the volume of gas. The finedroplets are vaporized when the droplets enter the gas inlet line 430when the entry point into the gas inlet line 430 includes a heatedelement 420, as shown in the exemplary aspect of FIG. 4. The heatedelement 420 may comprise any suitable space heating device, such as aheating coil. Because the droplets are very fine as a result of theultrasonic nebulization, the droplets will vaporize quickly uponentering the area heated by the heating element 420. Thus, as the heatedgas stream passes through the humidifying portion 400, the dry gas willbecome humidified from the evaporated fine droplets. The heating element420 may be sufficient to heat the volume of gas to the necessarytemperature, in which case additional heaters upstream or downstream ofthe humidifying portion 400 would not be necessary. However, because thehumidifying portion 400 injects humidifying agent droplets separatelyfrom the heating step, the heating step may be completely decoupled fromthe humidifying portion 400. In other words, in another aspect, theheating element 420 need not be present at the point where the dropletsenter the gas stream, but instead may be present in the gas inlet line430 upstream of the humidifying portion or in the discharge line 490downstream of the humidifying portion. In the case where the heating isperformed in the gas inlet line 430, the gas must be heated enough toevaporate the humidifying agent droplets.

The pulsing step of the aspect of FIG. 4 is analogous to the pulsingstep described above with respect to the aspect of FIG. 3. When it isdesirable to provide humidified gas to the patient 140, the amount ofhumidifying agent being delivered to the humidifying portion 400 will beimmediately increased. Simultaneously, the droplet generating device 470will be actuated. Thus, a rapid increase, or pulse, of humidifying agentdroplets will be delivered to a volume of gas traveling through the gasinlet line 430. Likewise, when it is desirable to reduce condensedhumidifying agent present in the discharge line 490, the delivering ofhumidifying agent to the humidifying portion 400 and/or the actuation ofthe droplet generating device 470 may be reduced or stopped. Thus, theamount of humidifying agent delivered to the volume of gas travelingthrough the gas inlet line 430 will be quickly reduced, thereby allowinga relatively dry volume of gas to continue through the discharge line490. As with the above-described aspects, when the dry gas streamcontacts condensed humidifying agent present in discharge line 490, thecondensed humidifying agent will be vaporized and carried with the gasstream through an expiratory limb 495. Alternatively, if the dry gaspicks up a sufficient amount of condensed humidifying agent tosufficiently humidify the dry gas, the gas may be delivered to thepatient instead of being exhausted.

The humidifying system of FIG. 4 may include a controller 460 andsensors 480, 482, 484, 486 may be implemented in a similar manner as inthe aspect of FIG. 3 in order to detect relevant system parameters andcontrol the flow of gas and humidifying agent in an optimal manner.Sensor 480 may be implemented to detect temperature and flow rate of thegas being delivered from the gas source 110, sensor 482 may beimplemented to detect flow rate, temperature, and pressure of thehumidifying agent being delivered to droplet generating device, sensor484 may be implemented to detect the level of humidifying agent, sensor486 may be implemented to detect the temperature of the heating element420, and sensor 488 may be implemented to detect the gas flow rate, gastemperature, relative humidity, and absolute humidity in the dischargeline 490. As illustrated in FIG. 4, the controller 460 is coupled toreceive information and control one or more of the gas source 110, thepump 440, the droplet generating device 470, and the heated element 420.The controller 460 may use some or all of the data detected from thevarious sensors to provide optimal control of any of the controllableparameters such as volume, rate of gas being delivered from the gassource, flow rate of humidifying agent to the droplet generating device470, rate of operation of the droplet generating device 470, andtemperature of the heated element 486. Furthermore, as discussed above,because the delivery of humidifying agent is decoupled from the heatingelement 420 (i.e. the heating element heats the gas/humidifying agentindependently of the delivery of the humidifying agent), the controller460 has more flexibility as to when to heat and when to deliverhumidifying agent.

The above-described aspects are directed to pulsing the delivery ofhumidifying agent in order to reduce condensation present in a dischargeline 365, 490. As described above, the pulsing method can be used ineach of the exemplary aspects illustrated in FIGS. 2 to 4. However, theaspects illustrated in FIGS. 3 and 4 also provide a method of deliveringhumidified gas to a patient 140. The method is carried out essentiallyin the same manner as described above, except that rather than removingcondensation from the discharge line 365, 490 by pulsing, the methodprovides a precise manner of delivering humidified gas to a patientwhile avoiding the disadvantages of a stationary water humidifier. Theelements of the method that are the same as described above aretherefore omitted. More specifically, the method of delivery uses thecontroller 360, 460 of FIGS. 3 and 4 to optimize the delivery ofhumidifying agent to the gas inlet line 390, 430 separately from pulsingthe gas flow.

The method of delivering humidified gas is the same as the methoddescribed above with respect to the pulsing method, except that thepulsing step is omitted. That is, the apparatus of FIGS. 3 and 4 areoperated by the controller 360, 460 to control the delivery ofhumidifying agent, among the other controllable parameters discussedabove, to deliver an optimized humidified gas. Thus, rather than sharplyreducing the amount of humidifying agent delivered to a volume of gas inorder reduce condensation, the method of delivering humidifying agentincludes flowing humidifying agent at a controlled flow rate to thehumidifier portion 300, 400 via a humidifying agent input line 350, 450.The delivery of humidifying agent is further optimized by using one ormore of the sensors 380, 382, 384, 386, 480, 482, 484, 486, 488. Thesensors detect the same parameters discussed above. The parameters areinputted to the controller 360, 460, and the controller 360, 460 thenadjusts the controllable variables discussed above to deliver aprecisely controlled amount of humidifying agent to a volume of gaswhile avoiding the problems of a stationary water humidifier. Asdiscussed above, in the aspect of FIG. 4, one of the controllablevariables may also be the rate of actuation of the droplet generatingdevice 470.

It is within the scope of the invention that any of the above aspectscan be duplicated within the same humidifying system 100 to providemultiple points of entry to introduce humidifying agent to therespiratory circuit 120. This is especially true with the aspect of FIG.4 because the production of fine droplets generally requires a low flowrate. Thus, for enough humidifying agent to be delivered to fullyhumidify the volume of gas traveling through the respiratory circuit120, several humidifying portions 400 may be implemented in a singlehumidifying system 100. In such systems, the controller 460 may be usedto synchronize and optimize the delivery of humidifying agent.

While aspects of the present invention have been described in a discretemanner to facilitate understanding, it is within the scope of theinvention that the aspects may be used in conjunction with each other.For example, the humidifying portions 200, 300, 400 illustrated in FIGS.2-4 may all be present in a single humidification system 100.Additionally, while the diverter 220 is illustrated only in FIG. 2, itis within the scope of the invention that the diverter 220 may be usedin conjunction with the aspects of FIGS. 3 and 4. In such a case, thecontroller 250, 360, 460 would control the diverter 220 in addition tocontrolling the other features.

Furthermore, it is within the scope of the invention that ahumidification system 100 may include multiple humidifying portions 200,300, 400 of the various types disclosed above. Additionally, the methodsdisclosed above may all be used within the same humidification system100. For example, in the aspects of FIGS. 3 and 4, the method of pulsingmay be used if condensation occurs in the discharge line 365, 490, whilethe method of delivering humidifying agent may be implemented during allother times.

The invention has been described herein with reference to variousspecific and preferred materials, embodiments and techniques. It shouldbe understood that many modifications and variations to such materials,embodiments and techniques will be apparent to those skilled in the artwithin the spirit and scope of the invention. Therefore, the inventionshould not be limited by the above description, and to ascertain thefull scope of the invention, the following embodiments should bereferenced.

All references cited herein are hereby incorporated by reference intheir entirety.

1. A method of reducing condensation in a respiratory circuit, themethod comprising: providing, during a patient inhalation cycle orimmediately after a patient exhalation cycle, a first amount ofhumidification agent to a first volume of gas being delivered from a gassource to a patient respiratory circuit; heating the humidificationagent or the first volume of gas to a temperature sufficient to maintainthe humidification agent in a vapor state when the humidification agentis combined with the first volume of gas; removing condensation from therespiratory circuit at least in part by providing, during a patientexhalation cycle or immediately after a patient inhalation cycle, asecond amount of the humidification agent to a second volume of gasbeing delivered from the gas source to the patient respiratory circuit,the second amount of the humidification agent being significantly lessthan the first amount of the humidification agent.
 2. The method ofclaim 1, wherein the respiratory circuit comprises at least one heaterelement and an inlet portion, a humidifying portion, and an outletportion, with the inlet portion upstream of the humidifying portion andthe outlet portion downstream of the humidifying portion; and heatingthe first or second volume of gas, using the at least one heaterelement, to facilitate removing the condensation before the first orsecond volume of gas passes through the humidifying portion, while thefirst or second volume of gas passes through the humidifying portion, orafter the first or second volume of gas exits the humidifying portion.3. The method of claim 2, further comprising: delivering the humidifyingagent directly onto the at least one heater element to vaporize thehumidifying agent while the first volume of gas is being delivered tothe patient respiratory circuit.
 4. The method of claim 3, furthercomprising: providing the first amount and the second amount of thehumidification agent using a pump; increasing a flow rate of the pump,from a first rate to a second rate, during the patient inhalation cycleor immediately after the patient exhalation cycle; and returning theflow rate of the pump to the second rate during a patient exhalationcycle or immediately after a patient inhalation cycle, without turningoff the pump.
 5. The method of claim 2, further comprising: providingthe first amount of humidification agent to the first volume of gas inpulsed intervals, a timing of the pulsed intervals being set so that avolume of gas containing a pulsed amount of the humidifying agent ispresent in the respiratory circuit at the same time the second volume ofgas is provided to the respiratory circuit.
 6. The method of claim 2,wherein the respiratory circuit further comprises a humidifying flowpath connecting the inlet portion to the outlet portion through thehumidifying portion, and a separate diverter flow path directlyconnecting the inlet portion to the outlet portion, and wherein theinlet portion comprises a diverter configured to direct at least aportion of a respective volume of gas traveling from the gas sourceeither to the humidifying flow path and through the humidifying portionto the outlet portion or to the diverted flow path and directly to theoutlet portion, wherein the method further comprises: actuating thediverter to direct the first volume of gas through the humidifying flowpath and the humidifying portion to the outlet portion during thepatient inhalation cycle or immediately after the patient exhalationcycle; actuating the diverter to direct the second volume of gas throughthe diverted flow path to the outlet portion during the patientexhalation cycle or immediately after the patient inhalation cycle. 7.The method of claim 6, further comprising: removing the condensationfrom the outlet portion, during the patient exhalation cycle orimmediately after the patient inhalation cycle, by actuating thediverter to switch the second volume of gas between the diverted flowpath and the humidifying flow path in pulsed intervals.
 8. The method ofclaim 7, wherein actuating the diverter in pulsed intervals causes thesecond volume to be split between the diverted flow path and thehumidifying flow path, with a greater amount of the second volume of gaspassing through the diverted flow path than through the humidifying flowpath.
 9. The method of claim 2, wherein the humidifying portioncomprises a droplet generating device, the droplet generating devicecomprising an ultrasonic vibrating plate configured to vibrate at anultrasonic frequency sufficient to nebulize a humidifying agent providedby a humidifying agent source to the humidifying portion of therespiratory circuit.
 10. The method of claim 9, wherein the humidifyingportion comprises a heating element, and a first sensor configured togenerate first sensor data indicative of a flow rate of the secondvolume of gas, a second sensor configured to provide second sensor dataindicative of a level of the humidifying agent in the humidifyingportion, and a third sensor configured to provide third sensor dataindicative of a humidity of in the outlet portion, wherein the methodfurther comprises: controlling a rate of operation of the dropletgenerating device based on the first sensor data, the second sensordata, and the third sensor data.
 11. A respiratory humidificationsystem, comprising: a respiratory circuit; and a controller, wherein thecontroller is configured to: provide, during a patient inhalation cycleor immediately after a patient exhalation cycle, a first amount ofhumidification agent to a first volume of gas being delivered from a gassource to the respiratory circuit; heating, state when thehumidification agent is combined with the first volume of gas, thehumidification agent or the first volume of gas to a temperaturesufficient to maintain the humidification agent in a vapor; removing,during a patient exhalation cycle or immediately after a patientinhalation cycle, condensation from the respiratory circuit at least inpart by providing a second amount of the humidification agent to asecond volume of gas being delivered from the gas source to therespiratory circuit, the second amount of the humidification agent beingsignificantly less than the first amount of the humidification agent.12. The system of claim 11, wherein the respiratory circuit comprises:at least one heater element; an inlet portion; a humidifying portion;and an outlet portion, the inlet portion being upstream of thehumidifying portion and the outlet portion downstream of the humidifyingportion; and wherein the controller is further configured to: cause theat least one heater element to heat the first or second volume of gas tofacilitate removing the condensation before the first or second volumeof gas passes through the humidifying portion, while the first or secondvolume of gas passes through the humidifying portion, or after the firstor second volume of gas exits the humidifying portion.
 13. The system ofclaim 12, wherein the respiratory circuit is configured to: deliver thehumidifying agent directly onto the at least one heater element tovaporize the humidifying agent while the first volume of gas is beingdelivered to the respiratory circuit.
 14. The system of claim 13,further comprising: a pump, wherein the controller is further configuredto: cause the pump to provide the first amount and the second amount ofthe humidification agent; increase a flow rate of the pump, from a firstrate to a second rate, during the patient inhalation cycle orimmediately after the patient exhalation cycle; and return the flow rateof the pump to the second rate during a patient exhalation cycle orimmediately after a patient inhalation cycle, without turning off thepump.
 15. The system of claim 12, wherein the controller is furtherconfigured to: provide the first amount of humidification agent to thefirst volume of gas in pulsed intervals, a timing of the pulsedintervals being set so that a volume of gas containing a pulsed amountof the humidifying agent is present in the respiratory circuit at thesame time the second volume of gas is provided to the respiratorycircuit.
 16. The system of claim 12, wherein the respiratory circuitfurther comprises: a humidifying flow path connecting the inlet portionto the outlet portion through the humidifying portion; and a separatediverter flow path directly connecting the inlet portion to the outletportion; and a diverter configured to direct at least a portion of arespective volume of gas traveling from the gas source either to thehumidifying flow path and through the humidifying portion to the outletportion or to the diverted flow path and directly to the outlet portion,wherein the controller is further configured to: actuate the diverter todirect the first volume of gas through the humidifying flow path and thehumidifying portion to the outlet portion during the patient inhalationcycle or immediately after the patient exhalation cycle; actuate thediverter to direct the second volume of gas through the diverted flowpath to the outlet portion during the patient exhalation cycle orimmediately after the patient inhalation cycle.
 17. The system of claim16, wherein the controller is further configured to: actuate, during thepatient exhalation cycle or immediately after the patient inhalationcycle, the diverter to switch the second volume of gas between thediverted flow path and the humidifying flow path in pulsed intervals, tocause removal of the condensation from the outlet portion.
 18. Thesystem of claim 17, wherein actuating the diverter in pulsed intervalscauses the second volume to be split between the diverted flow path andthe humidifying flow path, with a greater amount of the second volume ofgas passing through the diverted flow path than through the humidifyingflow path.
 19. The system of claim 12, further comprising: a dropletgenerating device associated with the humidifying portion, the dropletgenerating device comprising an ultrasonic vibrating plate configured tovibrate at an ultrasonic frequency sufficient to nebulize a humidifyingagent provided by a humidifying agent source to the humidifying portionof the respiratory circuit.
 20. The system of claim 19, furthercomprising: a heating element associated with the humidifying portion; afirst sensor configured to generate first sensor data indicative of aflow rate of the second volume of gas; a second sensor configured toprovide second sensor data indicative of a level of the humidifyingagent in the humidifying portion; a third sensor configured to providethird sensor data indicative of a humidity of in the outlet portion,wherein the controller is further configured to: control a rate ofoperation of the droplet generating device based on the first sensordata, the second sensor data, and the third sensor data.